Health care professionals have observed that certain arteries, such as the carotid arteries from the heart to the brain, can radiate sound waves, called bruits. Bruits can be detected using an examination with a stethoscope, and in severe cases, the bruits can be heard by a health care professional without a stethoscope by pressing their ear against the patient's neck. Early detection of bruits suggests treatment to prevent an embolism, which is a common cause of strokes.
For example, cholesterol, fat and minerals from the blood can be deposited on the inner arterial surface. When these materials build up, they can form plaques, for example, in and around the branching points of the carotid arteries. The branches closest to the heart can form the largest plaques. Plaque can cause great harm if it becomes large enough to pinch off the blood flow, which is referred to as a stenosis in the blood vessel. A plaque can also break off into the bloodstream and can be carried to the brain. Raised plaque may restrict the blood flow through the coronary artery and/or change the surface of the artery from a smooth surface to a rough surface, which can stimulate the formation of a blood clot. Blood clots can slowly build up and narrow the artery and eventually close off the artery to blood flow.
Moreover, the deterioration of arterial health appears related to the elastic properties of the large arteries near the heart. When healthy, these vessels are elastic and can stretch significantly with each pressure wave exerted by the heart. However, myocardial infarction can cause permanent damage to portions of the heart muscle by replacing it with scar tissue that will not contract, which affects the pumping action of the heart.
The detection of bruits resulting from blood vessel abnormalities, such as those discussed above, can be inconsistent. Sometimes a strong sound can be heard when there is little blockage; other times there is no bruit detected even though blockage is sever. Moreover, the human ear may only detect certain frequencies and volumes of sound that may or may not correspond to bruits that indicate a blockage.